Document backing surface for show-through and artifact reduction

Abstract

A document-backing surface for reducing show-through when a duplex-printed document is scanned but without producing undesirable artifacts. The document-backing surface has a plurality of first and second light-absorbing surfaces, and a plurality of specularly reflective surfaces partially covering each of the second light-absorbing surfaces. The first specularly reflective surfaces are oriented to reflect light from a scanner lamp to a scanner sensor. In an alternate embodiment, the document-backing surface is partially covered by a specularly reflective surface oriented to reflect light from the scanner lamp to the scanner lens. In another embodiment, the document-backing surface has a set of teeth, each of which has light-absorptive first and second tooth surfaces and a specularly reflective surface partially covering each second tooth surface. In addition, the present invention is directed to a method for using a document-backing surface.

Description

BACKGROUND OF INVENTION[0001]The present invention relates to document scanning and specifically to an apparatus that reduces show-through when a duplex-printed document (printed on both sides) is scanned but without producing undesirable artifacts such as black hole or black border.[0002]Various scanning technologies are used in document scanners, copiers, and facsimile machines (collectively, “document-scanning systems”) to convert documents into a digital image for copying, document distribution, or archiving. (Throughout this application, the term “document” means any material that may be scanned, such as paper, vellum, plastic, cardboard, photographs, or similar materials.) Generally, a scanner lamp illuminates a document, and a scanner sensor detects the reflection at a single point (such as a pixel) in the document. Scanning technologies measure the relative brightness (ranging from black to white) of each pixel reflection. The detected brightness is converted into an analog ...

AI Technical Summary

Benefits of technology

[0017]The present invention relates to document scanning, and specifically to an apparatus that reduces show-through when a duplex-printed document is scanned but without producing undesirable artifacts.

Problems solved by technology

With a duplex-printed document, however, the use of a white document-backing surface can create an inaccurate scanned image because the printing from the back side “shows through” and is visible in the scanned image.

But parameter adjustment causes some highlight color loss in copying map originals.

In addition, show-through can cause image-processing algorithms to fail.

This dependence on the printed pattern transmittance terms (Tf and Tb) is the cause of show-through in document scanning.

One drawback of the Knox references is that both sides of a document must be scanned.

A problem with a duplex scanning approach is that it is too costly to be practical.

Moreover, the image-processing algorithms are complex.

The Smith reference, however, suffers from all the problems (described below) that are inherent in the use of a black background.

The requirement for an estimating means increases the cost and complexity of the disclosed apparatus.

Further, the algorithm used in the estimating means is susceptible to failure which can cause false corrections, e.g., human eyes may be detected as holes and removed from the image.

One disadvantage of the Hulan reference is that it does not address the problem of show-through.

Another drawback is that holes, tears, and dog-ears may show up as black artifacts.

An additional limitation is that a means for identifying reference markings and operational components is required.

This increases the cost and complexity of the disclosed apparatus.

Because a white background is used for scanning, duplex documents scanned using the Rubscha reference may suffer from show-through.

A further disadvantage of the Rubscha reference is that it relies on moving parts, which are susceptible to mechanical breakdown.

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